The Contractor will investigate the following: The radiation dose dependency; the drug dose dependency; the effect of variations in time interval between application of radiation and of drugs; the occurrence of the effects in other tumors; the effect of combined treatment on skin and bone marrow; the conditions of potentiation on a cellular basis; the efficacy of other drugs in combination with radiation in selected systems for determination of therapeutic gain based on differential effect on normal and malignant cells (drugs of interest include vincristine, VM26, VP 12-213, daunomycin, and adriamycin(; and a study shall be made of different experimental tumors in order to analyze which of them are most suitable to be used in a panel for screening tumors which are resistant to conventional radiation therapy schedules.